Method for manipulating a dental virtual model, method for creating physical entities based on a dental virtual model thus manipulated, and dental models thus created

ABSTRACT

A 3D virtual model of an intra oral cavity in which at least a part of a finish line of a preparation is obscured is manipulated in virtual space by means of a computer or the like to create, recreate or reconstruct finish line data and other geometrical corresponding to the obscured part. Trimmed virtual models, and trimmed physical models, can then be created utilizing data thus created. The virtual models and/or the physical models may be used in the design and manufacture of copings or of prostheses.

This is a Continuation Application of U.S. patent application Ser. No.12/222,287, filed Aug. 6, 2008, which is a Continuation Application ofU.S. patent application Ser. No. 11/349,124, filed Feb. 8, 2006, anapplication claiming the benefit under 35 USC 119(e) of U.S. ProvisionalPatent Application No. 60/699,499, filed Jul. 15, 2005, the contents ofeach of which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to dentistry and in particular to computer-aidedmethods associated with prosthodontics.

BACKGROUND OF THE INVENTION

There are many procedures associated with the oral cavity in which aprecise three-dimensional representation of the cavity is very useful tothe dental practitioner.

Such representations enable the practitioner to study the cavity ofindividual patients in a similar manner to the study of the traditionalplaster model. More importantly, three-dimensional numerical entities ofthe dental cavity also allow the practitioner to study methods orapproaches when dealing with particular dental problems of any givenpatient, and for the design of physical entities in relation therewith.For example, in prosthodontics, a computer model of a patient's teethmay be manipulated to provide machining data to manufacture a physicalmodel of the intra oral cavity, and/or to design and manufacture acoping and/or a prosthesis.

A parameter used in the design and manufacture of a dental prosthesis,such as a crown or bridge, is the finish line, or transition boundarybetween the prosthesis and the dental preparation, and this needs to beprecisely defined in three-dimensions. Obtaining the finish linecoordinates from a computer virtual model is more efficient and oftenmore accurate than from a plaster cast, and moreover facilitates theproduction of such a prosthesis, for example via CNC machining, rapidprototyping, or other computerised technologies, if desired.

However, it is often the case that when scanning the intra oral cavityto obtain 3D data of the preparation and finish line on which thevirtual model is based, part of the finish line, and possibly also theshoulder and other parts of the preparation, may be obscured by softtissues such as the gum that, no longer being pushed by the dentalsurfaces that have been removed, deform to cover at least a part of thefinish line on the prepared dental site.

Additionally or alternatively, part or all of the finish line may beobscured by other agents, including, for example, accumulation of one ormore of saliva, blood, lubricant used with a dental drill, debrisresulting from working the dental site, and so on.

SUMMARY OF THE INVENTION

Herein, “dental material” refers to any material associated with dentalstructures of the intra oral cavity, including but limited to naturaldental materials such as for example enamel, dentine, pulp, dentalroots, and non-natural dental materials such as for example metallic andnon-metallic fillings, restorations, crowns, bridges, copings,preparations, and so on.

Herein, “dental clinic” refers to the interface between a dentalpractitioner and a patent, and thus includes any physical entity, inparticular a clinic, in which there is interaction between a dentalpatient and a dental practitioner. While “dental practitioner” typicallyrefers to a dentist, doctor or dental technician, it also includesherein all other caregivers, including for example dental surgeons,orthodontists, prosthodontists, or any other caregiver that may interactwith a dental patient during the course of a dental treatment, or thatmay be involved in determining, preparing or providing dental treatmentto a patient, particularly prosthodontic treatment. While “dentalpatient” or “patient” typically refers to a person requiring the dentalservices of a dental practitioner, it also includes herein any personregarding whom it is desired to create a 3D numerical model of the intraoral cavity thereof, for example for the purpose of practicing the sameor for carrying out research.

The term “prosthesis” is herein taken to include any restoration and anyonlays, such as crowns and bridges, for example, and inlays, such ascaps, for example, or veneering, or any other artificial partial orcomplete denture.

The term “virtual”, applied herein with respect to models, manipulationof models, and so on, for example, refers to being created, simulated,or carried out by means of a computer or computer network or the like.

While the term “preparation” typically refers to the stump and includingthe finish line and shoulder that is left of the tooth that is to bereplaced by the prosthesis—typically a crown—and on which the crown isto be mounted, the term herein also includes artificial stumps, pivots,cores and posts, or other devices that may be implanted in the intraoralcavity in such a position or in a position that is optimal forimplanting the crown.

The term “prosthodontic procedure” refers, inter alia, to any procedureinvolving the intraoral cavity and directed to the design, manufactureor installation of a dental prosthesis at a dental site within theintraoral cavity, or a real or virtual model thereof, or directed to thedesign and preparation of the dental site to receive such a prosthesis.

The term “numerical entity” is used herein synonymously with virtualmodel, 3D model, and other such terms, and relates to a virtualrepresentation in a computer environment of a real object, such as forexample a dentition or at least a part of intraoral cavity, or of a realmodel thereof.

The term “physical entity” is used herein to refer to a physical dentalobject included but not limited to a physical dental model of part orall of the dentition of the intraoral cavity including dies, a coping, aprosthesis, and so on.

The term “scanning” and its analogues refer to any procedure directed atobtaining 3D topographic data of a surface, particularly of a dentalsurface, and thus includes mechanical methods, typically based on 3Dprobes for example, optical methods, including for example confocalmethods, for example as disclosed in WO 00/08415, the contents of whichare incorporated herein in their entirety by reference, or indeed anyother method.

The terms “tool” and “machining tool” are taken herein to include anytool that is adapted for material removal, and may include inter aliamechanical tools such as drills for example, laser tools such as forexample laser drills or cutters, ultrasonic tools such as for exampleultrasonic cutters, and so on. Preferably, the machining paths andmaterial removal characteristics of such tools can be finely controlled,typically by computer means.

The present invention relates to a method for manipulating a virtualdental model, comprising:

(a) providing a 3D virtual model of at least a portion of an intraoralcavity comprising a preparation having a finish line, wherein at least aportion of the finish line is obscured;

(b) manipulating said 3D virtual model in the vicinity of said obscuredportion of said finish line in a virtual manner such as to create anauxiliary 3D virtual model corresponding to said obscured portion ofsaid finish line;

(c) providing topographical data of the finish line from the virtualmodel and the said auxiliary virtual model.

The virtual model may be provided by scanning the intra-oral cavity invivo, or by any other suitable method.

The finish line may be partially or fully obscured by any obscuringentity or matter, including, but not limited to, deformed soft tissues,accumulation of one or more of saliva, blood, lubricant used with adental drill, debris resulting from working the dental site, and so on.

The method can further comprise:

(d) identifying in said 3D virtual model a first virtual model partrepresenting a dental site comprising said preparation and a secondvirtual model part representing at least soft tissues in abuttingvirtual contact with said first virtual model part;

(e) manipulating said 3D virtual model such as to separate said firstvirtual model part from said second virtual model part;

(f) manipulating said first virtual model part such as to create saidauxiliary virtual model.

Step (d) may be carried out substantially in an automated manner whensaid 3D virtual model provided at step (a) comprises color dataassociated with 3D topographic data, wherein said identification of saidfirst virtual model part and said second virtual model part is based oncolor differences therebetween.

The second virtual model part may comprise said obscured portion of saidfinish line.

The step of manipulating said first virtual model part such as to createsaid auxiliary virtual model corresponding to said obscured part of saidfinish line may comprise:

(g) providing at least one cross section of said 3D virtual model alonga working plane inclined to the occlusion plane, at least within saidobscured finish line portion, said cross-section comprising a firstcross-section profile representing said preparation and a secondcross-section profile representing obscuring matter in abutting virtualcontact with said first cross-section profile at a contact region;

(h) extrapolating said first cross-section profile from said contactregion to provide a third cross-section profile representing at least anapproximation of a corresponding cross-section of said dental site belowsaid obscuring matter and identifying therein a corresponding element ofsaid obscured finish line portion.

By “extrapolating” is meant any suitable method, which may be numerical,graphical, intuitive, and so on, based on the first cross-sectionprofile.

Optionally, additional data relating to the emerging profile, gum lineand so on may also be provided.

In step (g), said at least one cross section of said virtual model maybe provided along a corresponding plane inclined generally orthogonallyto the occlusion plane.

Alternatively, the working planes may be parallel or non parallel one toanother, and/or at any desired angle to the occlusal plane.

Alternatively, any other method, for example any suitable graphicalmethod, may be used for defining the geometry of at least the obscuredfinish line portion.

The method optionally further comprises creating a trimmed first modelpart comprising said first model part and said auxiliary virtual model,and also manipulating said second model part to remove surface datathereof corresponding to said auxiliary virtual model and creating atrimmed second model part.

The said trimmed first model part can be further manipulated such as toinclude a virtual model base projecting therefrom, and said trimmedsecond model part can also be manipulated such as to include a modelwell substantially complementary to said model base. The virtual modelbase may optionally comprises a depth dimension extending substantiallyorthogonally to an occlusial plane of the intra oral cavity, and saidvirtual model base may of substantially uniform cross-sectional profilealong a depth thereof. Alternatively, the base may be convex-shaped,conical, fustoconical, or any other suitable shape.

The perimeter of the virtual base, when viewed along said depthdirection may correspond to any one of a finish line or demarcation lineof the trimmed first model. Alternatively, the perimeter of the virtualbase, when viewed along said plan direction, may correspond to any oneof circle, oval, polygon or any suitable shape.

Optionally, one of said virtual model base and said virtual model wellfurther comprises at least one virtual projection, and the other one ofsaid virtual model base and said virtual model well further comprises avirtual socket structure for virtually receiving said at least oneprojection. In other words, the virtual socket is substantiallycomplementary in form and size to the corresponding projection. Theprojection can also take the form of a laterally projecting tab that isreceivable in a socket structure that is formed as a longitudinalchannel on the side of the well.

The said at least one virtual projection and virtual socket structureare arranged with respect to said virtual base and virtual well suchthat said virtual base can be virtually received in said virtual well inonly one orientation with respect thereto.

The method optionally further comprises the step of preparing computerinstructions for controlling operation of a computer controlledmanufacturing machine for creating physical models corresponding to saidtrimmed first and second virtual model parts respectively including saidvirtual model base and said virtual model well. The said computerinstructions may be directed to carrying out a material removaloperation on at least one material blank to create said physical models,for example.

This material removal operation may comprise CNC (Computer NumericalControl) machining including milling of said at least one materialblank.

The present invention also relates to a method for manufacturing adental model, comprising:

(A) providing a trimmed first virtual model part and a trimmed secondvirtual model part, according to the invention, corresponding to atleast one dental site;

(B) preparing computer instructions for controlling operation of acomputer controlled manufacturing machine for creating physical modelscorresponding to said trimmed first and second virtual model partsrespectively including said virtual model base and said virtual modelwell; and

(C) executing said computer instructions on said computer controlledmanufacturing machine and creating a set of physical models comprising atrimmed first physical model part and a trimmed second physical modelpart corresponding to said trimmed first and second virtual model partsrespectively including said virtual model base and said virtual modelwell.

A dental site relates to a location in the intra oral cavity comprisingone or more teeth of interest. One or more such teeth may include apreparation.

The computer instructions may be directed to carrying out a materialremoval operation on at least one material blank to create said physicalmodels. The material removal operation may comprise CNC machining ofsaid at least one material blank.

The method for manufacturing a dental model may be applied to a singledental site, or alternatively to a plurality of dental sites on at leastone jaw of an intra oral cavity. Inn the latter case particularly, thetrimmed second virtual model corresponding to each said dental site canbe suitably joined in a virtual manner to provide a global virtual modelof said jaw. In such a manner it is possible to manufacture a model ofone or both partial of full jaws, in which any number of the teeththerein, whether or not they have a preparation, are formed as separatemodels which can be removed and replaced in the jaw model. Tooth modelsin cases where then tooth is complete or in which there is noobstruction can be manufactured in a similar manner as described above,mutatis mutandis, with the main differences that no recreation orreconstruction of obscured portions thereof need to be performed.

The invention also relates to a method for at least one of designing andmanufacturing a dental coping, using a trimmed first virtual modelaccording to the invention.

The invention also relates to a method for at least one of designing andmanufacturing a dental prosthesis, using a trimmed first virtual modelaccording to the invention.

The invention also relates to a physical model set of at least a portionof an intra oral cavity, comprising a trimmed first physical model partand a trimmed second physical model part corresponding to a trimmedfirst virtual model part and a trimmed second virtual model partaccording to the invention.

The present invention also relates to systems for manipulating virtualdental models and for manufacturing physical dental entities based on avirtual dental model manipulated according to the invention. Suchsystems may include a microprocessing unit comprising suitable softwarefor carrying out the method of the invention, an interface, such as forexample a mouse, tablet, keyboard and so on, a display, and a data inputmodule for inputting 3D data of the intra oral cavity.

Thus, according to the invention, a 3D virtual model of an intra oralcavity in which at least a part of a finish line of a preparation isobscured is manipulated in virtual space by means of a computer or thelike to create, recreate or reconstruct finish line data and othergeometrical corresponding to the obscured part. Trimmed virtual models,and trimmed physical models, can then be created utilizing data thuscreated. The virtual models and/or the physical models may be used inthe design and manufacture of copings or of prostheses.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 shows, by way of a flow chart, a method for manipulating a dentalvirtual model in accordance with an embodiment of the invention;

FIG. 2 shows various elements of a system used for providing andmanipulating a virtual dental model according to the invention.

FIG. 3 schematically illustrates a portion of the intra oral cavityrequiring a prosthesis.

FIG. 4 illustrates a virtual model of the intra oral cavity as viewedwith 3D attributes.

FIG. 5 illustrates the virtual model of FIG. 4 separated into a firstmodel part and a second model part.

FIG. 6 illustrates in plan view the first model part of FIG. 5 includinga plurality of planes normal to this view.

FIG. 7 illustrates a typical cross-section of the virtual first modelpart obtained along one of the planes in FIG. 6.

FIG. 8 illustrates the model parts of FIG. 5 after having been virtuallytrimmed according to the invention.

FIG. 9 illustrates a physical model of the intra oral cavity based onthe trimmed virtual model of FIG. 8.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A computer-based method for manipulating a virtual dental model,particularly useful for defining a finish line (also referred to hereinas “margin line”), according to the invention is illustrated in FIG. 1.Accordingly, acquiring an accurate 3D representation (herein alsoreferred to as “three-dimensional model”, “3D model”, “virtual model”and the like) of the intraoral cavity is the first step 110 that iscarried out by the method 100. This first virtual model is generallydesignated with the numeral 500 in the accompanying figures.

The target parts of the intraoral cavity that are to be scanned arefirst identified.

The target parts are the parts (also referred to interchangeably aszones or areas) of the intraoral cavity 200 which form the focus of aparticular dental procedure for a particular patient and regarding whichit is desired to obtain the 3D topographical or surface data thereof.The target parts typically include the part of the tooth or the teeth onwhich a particular prosthodontic procedure is to be performed, and insome cases may include partial or the full mandibular or maxillaryarches, or both arches. For example, the procedure may be aprosthodontic procedure involving a crown or bridge prosthesis to bedesigned and fabricated for fitting onto a preparation at a particulardental site.

The method of the invention may be applied after the dental site 250 hasbeen prepared, at least partially for a prosthesis. For a crownprosthesis, the dental site 250 includes a single tooth that is preparedfor receiving the prosthesis, while for a bridge prosthesis, there aretypically two dental sites, each of which includes a tooth that needs tobe prepared, in order to anchor the prosthesis. Referring to FIG. 3, thepreparation of each tooth requires the dental practitioner to perform adental material removal operation at the dental site 250, creating apreparation P having a central anchoring stump joined via shoulder T toa finish line S that circumscribes the stump and separates thepreparation from the emerging profile M, which in turn extends to thegum line G.

When the target area including the dental site 250 is scanned veryaccurately, it is possible for the internal surface of a correspondingcoping to be correspondingly accurately designed. Ancillary parts of theintraoral cavity are also typically included in the scan, and compriseparts of the adjacent and opposed teeth, principally teeth A, B, P', andoften to a lesser extent teeth A' and B' (which are adjacent to theopposite tooth P') or parts thereof. Typically, but not necessarily, theresolution of the scanned data for the ancillary parts may be less thanfor the dental site itself, since the manufacturing accuracy requiredfor the external surfaces of the crown prosthesis (the design of whichis dependent on the dental surfaces of the ancillary parts) may besubstantially less than for the internal surface of the coping (or ofthe crown if this is monolithic).

The present invention is particularly applicable to situations in whichat least a part of the finish line S and possibly a part of the shoulderT is obscured by other material 550, typically either soft tissue(typically gums) and/or a retraction wire (FIG. 4) and/or other foreignmatter. Thus, the virtual model 500 obtained by the scanning processlacks finish line data (and also emerging profile data) at the obscuredportions of the finish line.

The 3D digitized data of the intraoral cavity, including the dentitionand associated anatomical structures of a patient, may be provided usingany suitable equipment for scanning a patient's teeth. Referring to FIG.2, this is usually done at a dental clinic 22 by the dentist or otherdental practitioner. The dental clinic 22 is typically linked to one ormore dental labs 26, and possibly also to a dental service center 23 viaa communication means or network such as for example the Internet orother suitable communications medium such as an intranet, local accessnetwork, public switched telephone network, cable network, satellitecommunication system, and the like, indicated by the cloud at 24. Thedental lab 26 is particularly adapted for defining the finish line, aswell as for other tasks such as designing prostheses, designing andmanufacturing physical models of the dentition, and possibly also formanufacturing at least an external profile of the prostheses. The dentalservice center 23 is particularly adapted for manufacturing dentalhardware that requires a very high degree of precision, for exampleinner surfaces of prostheses that are required to match externalsurfaces of copings, and possibly also the copings themselves.

Such scanning equipment may include any suitable optical scanner, forexample, a hand-held scanner 31 that is used by the practitioner toacquire the 3D data.

Advantageously, a probe for determining three dimensional structure byconfocal focusing of an array of light beams may be used, for example asmanufactured under the name of CB-CAD or as disclosed in WO 00/08415,the contents of which are incorporated herein by reference in theirentirety. The 3D data obtained by the probe may then be stored in asuitable storage medium, for example a memory in a computer workstation32. Typically, the 3D data is sent over a suitable communication network24 to the dental lab 26, for further processing, as described below.Optionally, the to the dental service center 23 the 3D data may be sentvia communication network 24 to the dental lab 26, for the furtherprocessing.

Optionally, and preferably, color data of the intraoral cavity is alsoprovided together with the 3D data, and thus the virtual model comprisescoordinates and color information of the dental surfaces scanned.Examples of such scanners are disclosed in co-pending applicationentitled “METHOD AND APPARATUS FOR COLOUR IMAGING A THREE-DIMENSIONALSTRUCTURE”, filed on 17 Jun. 2005 and published under US 2006-0001739,and which is assigned to the present Assignee. The contents of theaforesaid co-pending application are incorporated herein by reference intheir entirety.

Alternatively, the clinic 22 may include equipment for obtaining anegative casting of a patient's teeth. In this case, the negative castor impression is taken of the patient's teeth, in a manner known in theart, and this negative model 33 is dispatched to one of the dental labs26 that is equipped to prepare from the negative model a positive cast34 suitable for scanning. The positive cast 34 may be scanned at thedental lab 26 by any method known in the art, including using theaforesaid probe manufactured under the name of CB-CAD or as disclosed inWO 00/08415. The 3D data is then transmitted over the network 24 to theservice center 23. Alternatively, the positive cast 34 may be dispatchedto the service center 23 by the dental clinic 22 and scanned at theservice center to obtain the 3D data. Alternatively, the service center23 produces a positive model 34 from the negative model 33 and isscanned thereat, or sent to the dental clinic 22 to be scanned thereat.Alternatively, the negative model 33 is scanned, either at the dentallab 26 or at the service center 23.

Alternatively, the negative model 33 provided by the clinic 22 is sentto the service center 23, either directly by the clinic 22, orindirectly via the dental lab 26, and a composite positive-negativemodel may be manufactured from the original negative model. Thereafter,the positive-negative model may be processed to obtain 3D digitizeddata, for example as disclosed in U.S. Pat. No. 6,099,314, assigned tothe present Assignee, and the contents of which are incorporated hereinin their entirety.

Alternatively, the 3D digitized data may be obtained in any othersuitable manner, including other suitable intra oral scanningtechniques, based on optical methods, direct contact or any other means,applied directly to the patient's dentition. Alternatively, X-ray based,CT based, MRI based, or any other type of scanning of the patient or ofa positive and/or negative model of the intra-oral cavity may be used.The dimensional data may be associated with a complete dentition, or ofa partial dentition, for example such as a preparation only of the intraoral cavity.

Once the 3D digitized data is obtained, the next steps 120-126, whichare performed with the aid of a suitable computer, enable the fullfinish line S to be defined, which enables the subsequent design andmanufacture of an appropriate dental prosthesis, step 170, to befollowed by the installation of the appliance in the oral cavity of thepatient, step 180. These steps are generally carried out in the dentallab 26, though may be executed at the dental clinic 22 or service center23 with the appropriate equipment and expertise.

Referring to FIG. 1 and FIG. 5, in step 120 the virtual model 500 ismanipulated by means of a suitable computer in order to separate a firstpart 510 of the virtual model representing the dental site 250, inparticular the hard tissues thereof, from a second part 520 of thevirtual model, typically the remainder of the model 500, and includingat least the data representing the soft tissues and possibly foreignmatter such as retraction wires, etc, that surround the first part 510.Thus, this step isolates the surface data corresponding to the parts ofthe emerging profile M, the portion S1 of finish line S and preparationP that are not obscured by soft tissue or foreign objects including, forexample, saliva, blood, lubrication fluid, debris and so on. This stepmay be performed manually with a computer, typically interactively, by auser, by means of suitable graphics software, for example, that displaymodel 500, and an interface such as a mouse, keyboard, and so on, forexample. The user may visually identify a demarcation profile D (FIGS. 4and 5) that separates model parts 510 and 520, and for this purpose themodel 500 as displayed may be manipulated and viewed at any attitude,rotational angle, magnification etc. as desired. Suitable software formanipulating a virtual model in this manner are well known in the artand will not be described further herein. Then, the user virtually marksa number of points on the displayed model 500 which are converted by thecomputer into corresponding 3-dimensional coordinates of the demarcationprofile, and suitable interpolation between points completes thedefinition of the demarcation profile D. Then, the computer can dividethe model 500 along profile D into model parts 510 and 520.

Alternatively, and particularly when the virtual model 500 alsocomprises color data corresponding to the topographical data, the colordifferences between the relatively white hard dental surfaces of thedental site 250 and the relatively pink/red gum tissue and/or theretractor wire or other foreign matter, may be used to separate themodel 500 into model parts 510 and 520 in an automated manner. Examplesof such methods are disclosed in co-pending application entitled “METHODFOR PROVIDING DATA ASSOCIATED WITH THE INTRAORAL CAVITY”, filed on 17Jun. 2005 and published under US 2005/0283065, and which is assigned tothe present Assignee. The contents of the aforesaid co-pendingapplication are incorporated herein by reference in their entirety.

In the next step 122, and referring also to FIGS. 5 and 6, the exposedportions S1 of the finish line S, i.e., the portions that are visible,are identified and marked in the first model part 510. By “marking” isincluded that an attribute is added to the data points corresponding tothese portions of the model 510, so that these portions may behighlighted and/or further manipulated, displayed etc. as a unit. Thisidentification and marking may be done manually, by means of a displayand interface, similarly to that described for step 120 above, mutatismutandis. Alternatively, for example, this may be accomplished in anautomated manner, or at least semi-automated manner, by suitablymanipulating the first model part 510 by means of a suitable algorithmor the like. For example, the computer in which the method is beingexecuted may be programmed to identify within the data of the firstmodel part 510, relatively sharp changes in geometry, as is the case inthe change of cross-sectional profile between the emerging profile M,the finish line S and shoulder T. Alternatively, other rules may beincorporated to provide the exposed portions S1 of the finish line S.

In the next step 124, the areas of the first model part 510 that do notinclude a finish line are identified and optionally marked. Thisidentification and marking may be done manually, by means of a displayand interface, similarly to that described for step 122 above, mutatismutandis. Alternatively, the computer may attempt to determine in whatmanner the exposed portions S1 does not complete a closed geometricalform, and thus determines which parts of the geometric form are“missing”. The computer can then compute in an automated manner whichpart of the 3-dimensional space generally occupied by the first modelpart 510 would include these “missing” parts.

In any case, once the missing portions, herein generally designated as515, are identified and optionally marked in a suitable with referenceto the first model part 510, the next step 126 is to create3-dimensional representations of the missing portions 515, i.e., a thirdmodel part. This can be accomplished in a number of different ways. Forexample, and referring to FIGS. 6 and 7, the virtual model 500 is slicedabout a plurality of working planes X_(N) to provide a correspondingplurality of cross-sections C_(N) of the model 500. Thesecross-sectional planes X_(N) are typically orthogonal to the occlusalplane, and preferably pass approximately through the center portion PCof the preparation P. The plurality of planes may span an arc as viewedfrom above the dental site (FIG. 6) such as to include the full missingportion 515 and extend at least a little beyond the same to include atleast two cross-sectional profiles that fully include emerging profile Mdata, finish line S data, preparation P data, gum line G data, plus gumGM data.

A typical cross-section C_(N) is illustrated in FIG. 7, and shows theprofile of the model 500, including first model part 510, second modelpart 520, and demarcation line D. Based on the user's experience andskill, the user can extrapolate where he or she considers that at leastone or more of the missing finish line S2 _(N) data, missing emergingprofile data M2, missing preparation data P2, and missing gum line dataG2 data may be in relation to this cross-section. These missing data canthen be input to the computer in which the manipulations are beingcarried out, for example by “clicking” with a mouse or by means of atablet, or by any other computer aided means, at locations on thedisplayed cross-section where the extrapolations are to be made. Suchextrapolations may be made by the user, utilizing experience andjudgment as to where the missing profile may be. Alternatively, theuser, knowing what type of tool was used for creating the preparation,may have a fair idea of the profile of the finish line cross section.For example, the finish line may be of any type thereof, for exampleknife edge, feather edge, chamfer, chamfer bevel, shoulder, shoulderbevel, and so on. Alternatively, the finish line may comprise acombination of different types around the periphery of the preparation,for example part of the finish line for a particular preparation may beknife edge, while another part may be feather edge. According to thetype of finish line the user is expecting to find, the same type ofprofile may be applied to the missing section, and subsequentlymodified, manually or automatically using any suitable matching,smoothing, graphical or other type of algorithm to fit as required.

When this operation has been repeated for all the cross-sections, a3-dimensional virtual third model part 530 corresponding to theextrapolated data may be created by the computer by properly integratingthe created data, and the user may view the results together with orseparately from the first model part 510.

Alternatively, the planes X_(N) may be at any orientation and at anyposition with respect to the virtual model 500.

Alternatively, the missing portions may be virtually extrapolated usingany suitable graphic based technique, for example, or in any othersuitable manner.

In other cases, it is possible for a number of portions of the finishline to be obscured, and these portions are each treated as describedabove, mutatis mutandis in order to extrapolate and obtain the missing3D data.

In some cases it is possible that the full extent of the finish line Sis in fact obscured, and in such cases the method of the invention isapplied for the full perimeter around the preparation P in a similarmanner to that described above, mutatis mutandis, the main differencelying in that the sections C_(N) would need to intersect the fullperimeter circumscribing the preparation P.

In other case, it is possible for the finish line S to be exposed, butfor a part or all of the emerging profile to the obscured. Again, thesame method as above may be employed to obtain the missing 3D data,mutatis mutandis.

Alternatively, step 126 may be performed in a fully automated or semiautomated manner, and suitable algorithms and/or rules such asgeometrical rules may be formulated for this purpose. In any case,according to the invention, the third model part 530 may be refined overand over again until a suitable result is achieved. At each iteration,the user may inspect the third model part 530, and perhaps finely tunecontrol parameters of the algorithm, for example, to arrive at a bettersolution.

In the next step 130, the third model part 530 is combined together withthe first model part 510 in a virtual manner to create a completedtrimmed virtual first model part 540 of the dental site, including afully defined finish line S and preferably also a complete emergingprofile M.

In the next step 140, and referring to FIG. 8, the second model part 520is converted to a trimmed second model part 570 by manipulation thereofso as to effectively remove thereof excess surface data 560 thatcorresponds to the third model part 530, i.e., that would be superposedalong a particular direction Z when joining the complete virtual model540 to the second model part 520 such that the data corresponding to thefirst model part 510 in said trimmed first model part 540 “fits” in thesame position as before with respect to the second model part 520.Direction Z is typically substantially orthogonal to the occlusionplane. The trimmed second model part 570 thus joins, at new demarcationline DN (at least along direction Z), the trimmed first model part 540to form a new virtual model 590 in which the finish line S, emergingprofile P, gum line G and preparation P are now fully defined.

For the case of a bridge prosthesis, the procedure may be repeated, ifrequired, for each of the anchoring teeth.

The method of the invention may be further extended to the manufactureof a physical dental model that may be used in the design and/ormanufacture of a prosthesis, for example a crown or bridge prosthesis.Thus, in step 150, the trimmed first virtual model part 540 is modifiedto include a virtual base portion 544, typically having across-sectional profile identical to a plan cross-section of thecomplete virtual model 540 as viewed in direction Z (FIG. 9). Then,machining instructions, typically CNC milling instructions, butalternatively including any suitable computer instructions for acomputer controlled material removal machine, for a material removaloperation are created based on the thus modified trimmed first modelpart 540. The machining instructions may be further modified to includeinstructions for forming alignment plug members 545 extending from thebottom part of the base portion 544.

Similarly, in step 150 the trimmed second model part 570 is modified toinclude a well portion 574, typically having a cross-sectional profileidentical to a plan view of the new demarcation line DN as viewed indirection Z, and machining instructions, typically CNC millinginstructions, but alternatively including any suitable computerinstructions for a computer controlled material removal machine, for amaterial removal operation are created based the thus modified trimmedsecond model part 570. Alternatively, in another aspect of theinvention, rather than material removing instructions, computerinstructions for creating a physical model using rapid prototypingtechniques may instead be created. The machining instructions may befurther modified to include instructions for forming alignment sockets574 complementary to receiving members 545.

In general, the shape of the demarcation line, in plan or occlusal view,is asymmetric, and therefore the trimmed first model part 540 willgenerally fit in the trimmed second model part 570 in only one, thecorrect, orientation. Thus, in many cases it is possible to do withoutthe plug members 545 and alignment sockets 574.

In any case, the base portion 544 is generally complementary to the wellportion 574.

Alternatively, the trimmed first model part 540 may be based on thefinish line, rather than the demarcation line, so that in plan view theouter profile of the trimmed first model part 540 corresponds to thefinish line. Similarly, the profile of the well portion 574 in plan viewalso corresponds to the finish line, or close thereto to allow a smallclearance between the trimmed first model part 540 and the trimmedsecond model part 570.

Alternatively, the trimmed first model part 540 may base portion 544that is a independent of the finish line or the demarcation line, butrather circumscribes both, so that in plan view the outer profile of thetrimmed first model part 540 may comprise, for example, a circle, oval,polygon, and so on. Similarly, the profile of the well portion 574 inplan view also generally corresponds to outer profile of the trimmedfirst model part 540. When the outer profile of the trimmed first modelpart 540 comprises a symmetrical shape, it may be necessary to includeplug members 545 and alignment sockets 574.

Once the computer based instructions for creating the physical modelsare ready, the physical models corresponding to the trimmed first modelpart 540 and the trimmed second model part 570 may be created in acorresponding manner.

To manufacture a prosthesis such as a crown or a bridge, for example,the lab technician requires two physical jaws models mounted on anarticulator or placed in the correct spatial orientation one against theother. According to the present invention, the computer controlledmaterial removal instructions also take into consideration also thespatial relation between the two jaws and their occlusion, for exampleas disclosed in WO 2004/030565 assigned to the present Assignee, and thecontents of this publication are incorporated herein in their entirety.

In the next step 160, a material removal operation is performed by acomputer aided removal operation machine having a suitable machiningtool, using any suitable CAM (Computer Aided Manufacturing) technology,typically a CNC milling machine, on a blank of material. This materialis typically plaster or any other type of material commonly used fordental models, however any other suitable material may be used.Alternatively, other techniques may be used, for example rapidprototyping, for creating the physical models. Accordingly, a physicalmodel of the two jaws or at least a part of each of the two jawscorresponding to the virtual model 500 is manufactured, together withsuitable alignment structures that ensure the proper occlusionrelationship between the two components of the model representing thetwo jaws or the two jaw fragments.

At this point, the technician has his necessary physical model and canproceed with making the crown or the bridge.

Optionally, the physical model may be designed and manufacturedcomprising a plurality of individual detachable tooth models, includingthe target tooth, and any one or more of the surrounding and facingteeth. Similarly, when providing a physical model for use in connectionwith a bridge, the tooth models of one or both of the anchor teeth maybe detachable from the model jaw (partial or full), and optionally, anyone or more of the surrounding and facing teeth may also be detachable.When more than one tooth is detachable in the model, it is ensured thatthe profile of the base portion for each detachable tooth model issufficiently different from the other base portions, and/or differentplug member/alignment socket arrangements are used, to reduce thepossibility of the wrong tooth model being matched with a particularwell.

In step 170, and based on information from the virtual 3D image, thedentist or a technician may generate a 3D virtual prosthesis model of acrown to be fitted on a tooth stump or of a bridge to be fitted on thetooth surface, to generate a digital file. Alternatively, the outersurface of the prosthesis may be designed manually if desired.Optionally, and typically, the prosthesis model may also include avirtual model of a coping plus a virtual model of a cap that is to bemounted onto the coping. The coping may be manufactured using anysuitable method, for example as disclosed in WO 2004/087000, alsoassigned to the present Assignee, and the contents of which areincorporated herein in their entirety. The cap or full prosthesis may bemanufactured using any suitable method, for example as disclosed in U.S.Ser. No. 11/046,709 or in U.S. Provisional Application No. 60/632,350,also assigned to the present Assignee, and the contents of which areincorporated herein in their entirety.

In the final step, the prosthesis may be installed in the oral cavity ofthe patient.

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

Finally, it should be noted that the word “comprising” as usedthroughout the appended claims is to be interpreted to mean “includingbut not limited to”.

While there has been shown and disclosed exemplary embodiments inaccordance with the invention, it will be appreciated that many changesmay be made therein without departing from the spirit of the invention.

1. A computerized method for reconstructing data associated with anobscured finish line using a computer system, comprising: (a) providingto a computer processor, data of a 3D virtual model of at least aportion of an intraoral cavity comprising a preparation having a finishline, the finish line defining a transition boundary between thepreparation and a prosthesis that may be mounted with respect to thepreparation, wherein at least a portion of the finish line is obscured;and configuring the computer processor to: (b) manipulate said data ofsaid 3D virtual model in a vicinity of said obscured portion of saidfinish line in a virtual manner to create an auxiliary 3D virtual modelthat is displayable on a computer screen and corresponds to saidobscured portion of said finish line, and (c) provide topographical dataof the finish line from the 3D virtual model and the auxiliary 3Dvirtual model to reconstruct data of the obscured finish line.
 2. Themethod according to claim 1, further configuring said processor to: (d)identify in said 3D virtual model a first virtual model partrepresenting a dental site comprising said preparation and a secondvirtual model part representing at least soft tissues in abuttingvirtual contact with said first virtual model part; (e) manipulate said3D virtual model to separate said first virtual model part from saidsecond virtual model part; and (f) manipulate said first virtual modelpart to create said auxiliary 3D virtual model.
 3. The method accordingto claim 2, wherein step (d) is carried out substantially in anautomated manner when said 3D virtual model provided at step (a)comprises color data associated with 3D topographic data, wherein saididentification of said first virtual model part and said second virtualmodel part is based on color differences therebetween.
 4. The methodaccording to claim 2, wherein said second virtual model part comprisessaid obscured portion of said finish line.
 5. The method according toclaim 3, further comprising creating a trimmed first model partcomprising said first virtual model part and said auxiliary 3D virtualmodel.
 6. The method according to claim 5, comprising furthermanipulating said second virtual model part to remove surface datathereof corresponding to said auxiliary 3D virtual model and creating atrimmed second model part.
 7. The method according to claim 6, furthercomprising manipulating said trimmed first model part to include avirtual model base projecting therefrom, and manipulating said trimmedsecond model part to include a virtual model well substantiallycomplementary to said virtual model base.
 8. The method according toclaim 7, wherein said virtual model base comprises a depth dimensionextending substantially orthogonally to an occlusal plane of the intraoral cavity, and wherein said virtual model base is of substantiallyuniform cross-sectional profile along a depth thereof.
 9. The methodaccording to claim 8, wherein said virtual model base comprises aperimeter when viewed along said depth dimension corresponding to anyone of a finish line or demarcation line of the trimmed first model. 10.The method according to claim 8, wherein said virtual model basecomprises a perimeter, when viewed along a plan direction, selected fromthe group consisting of a circle, an oval, and a polygon.
 11. The methodaccording to claim 7, further wherein one of said virtual model base andsaid virtual model well further comprises at least one virtualprojection, and the other one of said virtual model base and saidvirtual model well further comprises a virtual socket structure forvirtually receiving said at least one projection.
 12. The methodaccording to claim 11, wherein said at least one virtual projection andvirtual socket structure are arranged with respect to said virtual modelbase and virtual model well such that said virtual model base can bevirtually received in said virtual model well in only one orientationwith respect thereto.
 13. The method according to claim 7, furthercomprising the step of preparing computer instructions for controllingoperation of a computer controlled manufacturing machine for creatingphysical models corresponding to said trimmed first and second virtualmodel parts respectively including said virtual model base and saidvirtual model well.
 14. The method according to claim 13, wherein saidcomputer instructions are directed to carrying out a material removaloperation on at least one material blank to create said physical models.15. The method according to claim 14, wherein said material removaloperation comprises CNC machining of said at least one material blank.